In this work, an adaptive rule based Energy Management System (EMS) is proposed for Electric Vehicles (EVs) using Battery/Supercapacitor (SC) based Hybrid Energy Storage System (HESS). Rules for the EMS are designed considering SC State Of Charge (SOC), vehicle acceleration and battery threshold power. A continuous power distribution factor which depends upon battery SOC is added to improve the performance of the rule based framework. The impact of practical uncertainties such as vehicle mass variation, road slope variation and variation in both mass and slope are also analysed to test the efficiency and practicality of the proposed controller. A battery State Of Health (SOH) model is applied to test the ageing stress over battery under different uncertain conditions. A real time simulator OPAL-RT is used to implement the proposed EMS. Simulation results show reduction of battery current by the proposed EMS as compared to Filter based strategy and Battery only EV undergoing conditions of varying vehicle mass, varying road slope, varying vehicle mass and road slope both for US06 and SC03 drive cycle. Hence robustness of the proposed rule based EMS is established ensuring enhanced participation of the SC in HESS leading to improvement in battery life and vehicle performance.